Actinobacteria isolated from wastewater treatment plants located in the east-north of Algeria able to degrade pesticides

Influence of cadmium and zinc contamination on the sediment microbiome of estuarine and coastal ecosystems in the Southwest Coast of India

Metals and their nanoparticles can induce toxicities that influence the survival of both microorganisms and macroorganisms. The current study reports on the impact of heavy metal pollution on the microbiome of estuarine and coastal sediments, where the settling and final remineralization of organic matter occur. Sediment samples collected from the Cochin estuary along the southwest coast of India and its adjacent coast showed high concentrations of cadmium (Cd) and zinc (Zn). The contamination factor (CF), calculated by comparing the concentration of metals in each station with that of shale value for Cd and Zn, ranged from 5.2 to 8.7 and 1.5 to 2.0 respectively, in the estuarine and coastal stations. Microbiome analysis revealed that bacteria were common across all stations but varied in relative abundance. Proteobacteria, Chloroflexi, Actinobacteria, Desulfobacteria, and Acidobacteria were the major bacterial phylum found in all stations. More than 70% of the bacteria were tolerant to 1 mM concentration of Cd. The findings of our study suggest that metal pollution can influence the microbiome of sediments in the estuaries and coasts. Bacteria with metal tolerance may dominate in polluted areas, but their participation in remineralization may be impaired, as evident in our previous reports. This impairment could ultimately influence the dynamics of the food web and the biogeochemical cycling of nutrients, necessitating further research.

Assessment of nitrification process in a sequencing batch reactor: Modelling and genomic approach

Nitrification of ammoniacal nitrogen (N-NH4+) to nitrate (N-NO3-) was investigated in a lab-scale sequencing batch reactor (SBR) to evaluate its efficiency. During the nitrification process the removal of N-NH4+ reached 96%, resulting in 73% formation of N-NO3-. A lineal correlation (r2 = 0.9978) was obtained between the concentration of volatile suspended solids (VSS) and the maximal N-NO3- concentration at the end of each batch cycle under stationary state. The bacterial taxons in the initial inoculum were identified, revealing a complex diverse community mainly in the two major bacterial phyla Proteobacteria and Actinobacteria. The FAPROTAX algorithm predicted the presence in the inoculum of taxa involved in relevant processes of the nitrogen metabolism, highlighting the bacterial genera Nitrospira and Nitrosomonas that are both involved in the nitrification process. A kinetic model was formulated for predicting and validating the transformation of N-NH4+, N-NO2- and N-NO3- and the removal of organic and inorganic carbon (TOC and IC, respectively). The results showed how the increase in biomass concentration slowed down the transformation to oxidised forms of nitrogen and increased denitrification in the settling and filling stages under free aeration conditions.

Biodegradation of neonicotinoid insecticide acetamiprid by earthworm gut bacteria Brucella intermedium PDB13 and its ecotoxicity

Extensive use of neonicotinoid insecticides in recent decade had contaminated water and soil systems and poses serious environmental and health risk. Microbial degradation of toxic contaminants in the environment has been established as a sustainable tool towards its remediation. Under this context, the present study focused on the biodegradation of neonicotinoid insecticide acetamiprid, by bacterial strain Brucella intermedia PDB13 isolated from the gut of the acetamiprid exposed earthworms. To enhance acetamiprid biodegradation, suitable parameters such as pH, temperature, inoculum size and acetamiprid concentration range were optimised using Response Surface Methodology (RSM). The experimental results showed that the Brucella intermedium PDB13 can tolerate and degrade relatively high concentrations of acetamiprid (50 - 350 mg L^-1). The results confirmed that maximum degradation of about 89.72% was achieved under optimized conditions. Further, confirmation of acetamiprid biodegradation was assessed through the occurrence of its degraded metabolites through HPLC, FTIR, and LCMS analysis. Based on this analysis, possible acetamiprid biodegradation pathway by Brucella intermedia PDB13 was proposed. Additionally, cytotoxicity, earthworm acute toxicity, and zebrafish embryo toxicity studies were also performed to assess the toxicity variations between the parent compound and its metabolites. The acetamiprid treated group resulted in cytotoxic effects apparently, with the increase in aberrant cells frequency (22.5 ± 3.3), when compared with its metabolites (2.3 ± 4.3) and control (1.9 ± 5.6) respectively. All these results evidently reported the degradation potential of Brucella intermedia PDB13, thereby establishing the scope for further advanced biodegradation studies towards mitigating the pesticide pollution.

Biodegradation and Metabolic Pathway of the Neonicotinoid Insecticide Thiamethoxam by Labrys portucalensis F11

Thiamethoxam (TMX) is an effective neonicotinoid insecticide. However, its widespread use is detrimental to non-targeted organisms and water systems. This study investigates the biodegradation of this insecticide by Labrys portucalensis F11. After 30 days of incubation in mineral salt medium, L. portucalensis F11 was able to remove 41%, 35% and 100% of a supplied amount of TMX (10.8 mg L^-1) provided as the sole carbon and nitrogen source, the sole carbon and sulfur source and as the sole carbon source, respectively. Periodic feeding with sodium acetate as the supplementary carbon source resulted in faster degradation of TMX (10.8 mg L^-1); more than 90% was removed in 3 days. The detection and identification of biodegradation intermediates was performed by UPLC-QTOF/MS/MS. The chemical structure of 12 metabolites is proposed. Nitro reduction, oxadiazine ring cleavage and dechlorination are the main degradation pathways proposed. After biodegradation, toxicity was removed as indicated using Aliivibrio fischeri and by assessing the synthesis of an inducible β-galactosidase by an E. coli mutant (Toxi-Chromo test). L. portucalensis F11 was able to degrade TMX under different conditions and could be effective in bioremediation strategies.